The present invention relates to devices for developing a bore in bone tissue and, more particularly, to drill bits for creating a hole in a selected osteochondral site. The invention also relates to the use of the drill bits to create a hole in a selected osteochondral site.
The drill bit of the present invention can also be used or adapted for use with other tissue surfaces having components of varying hardness, (e.g., periosteum, bone, cartilage and/or other attached elastic materials).
Articular cartilage, especially of the hips, knees, shoulder, and ankle, are subject to high wear rates over time, which may cause degradation of cartilage tissue. Trauma along with disease, are also players contributing to the damage and degeneration of articular cartilage. To repair these defect sites, typically, a cylindrical hole of a desired diameter (or holes, potentially, depending on the size of the defect) is formed at the site of the damage. The holes have in the past been formed using instruments such as punches, twist drill bits, end mill style bits, and reamers. The excised hole is then filled with a replacement graft, either biological or synthetic, having a diameter generally corresponding to the diameter of the hole.
As indicated, the use of drill bits for the creation of holes in osteochondral tissue is known. However, problems can occur with existing osteochondral drill bits when drilling through bone and cartilage. The properties of the overlaying cartilage, subchondral bone, and trabecular bone all must be considered to ensure a clean well cut hole. The toughness and elasticity of cartilage and the extremely hard subchondral bone makes drilling/reaming/punching a clean, well-cut hole at the desired location difficult. The open-celled structure of trabecular bone is prone to crushing and/or undesired chipping with the advancement of instruments. When drilling, it has been known for drill bits to create a ragged, unclean, imprecise hole as well as to impose trauma to surrounding tissue.
Particularly large defects sites, requiring larger instrumentation, may further amplify these problems. Impacting a large diameter punch into an osteochondral site spreads the force over a large area. Spreading the concentration of this force over the large area increases the puncture force required for penetration. This can cause unwanted fracturing of the subchondral bone, as well as, rolling of the cartilage over the lip around the hole wall.
Thus, there exists a need for improved instrumentation that overcomes these limitations.